Japanese Patent Application Laid-Open Publication No. 2006-312901 discloses a conventional fuel feeding device for a gas engine. In this fuel feeding device, a cutoff valve for blocking the supply of fuel to the gas engine when the gas engine is stopped is provided between a primary regulator and a secondary regulator.
A small-sized cassette tank charged with butane gas is connected to an entrance of the fuel feeding device described above. An exit of the fuel feeding device is connected to a fuel nozzle that is attached to a mixer which in turn is connected to an air intake port of the gas engine.
The fuel feeding device is provided with a vaporizer, a primary regulator, a cutoff valve, and a secondary regulator that are provided in sequence in the direction from the fuel entrance to the fuel exit. The crankcase, air intake port, or other negative-pressure portion of the gas engine is connected to the cutoff valve.
Negative pressure does not occur in the negative-pressure portions when the gas engine is stopped, and the cutoff valve is therefore closed, but when a piston of the gas engine moves and a negative pressure occurs in a negative-pressure portion of the gas engine, the cutoff valve is opened by this negative pressure, and the fuel in the small-sized tank flows to a fuel feeding passage that is past the vaporizer.
FIGS. 10A through 10D hereof show an operation of the conventional fuel feeding device for a gas engine described above, the vaporizer not being shown in the drawings.
In FIG. 10A, when a manual stopcock 202 provided to a fuel feeding passage 201 is opened, the fuel passes from a fuel tank 203 to the gas engine 211 through a primary regulator 204, a cutoff valve 206, a secondary regulator 207, and a mixer 208, as indicated by the arrow A, and the gas engine 211 becomes operative.
FIG. 10B shows a state in which the gas engine is stopped. A vacuum modulator 212 of the primary regulator 204 is closed, and the cutoff valve 206 is also closed. The manual stopcock 202 remains open at this time.
In FIG. 10C, when the outside air temperature decreases during the night, for example, and the pressure on the downstream side decreases below that of the vacuum modulator 212 of the primary regulator 204, the vacuum modulator 212 opens, and liquefied gas fuel 213 flows out from the fuel tank 203. When the outside air temperature is 0° C. or lower, for example, the liquefied gas fuel 213 is in liquid form, and penetrates into the primary regulator 204 and the fuel passage 214 between the primary regulator 204 and the cutoff valve 206.
In FIG. 10D, when the outside air temperature changes in the afternoon, for example, from the state shown in FIG. 10C so as to exceed 0° C., the liquefied gas fuel 213 changes to a gas, and the pressure inside the primary regulator 204 and the fuel passage 214 therefore increases.
As a result, a high pressure acts on the vacuum modulator 212 or the cutoff valve 206, making it difficult for these components to open, and the gas engine becomes difficult to start. Even when the vacuum modulator 212 or the cutoff valve 206 does open, the mixture fed to the gas engine is highly concentrated, and it is thus difficult for the ability of the gas engine to start to improve.
Multi-purpose engines that use gas fuel are often used in a manner that involves frequent movement to perform work, and therefore must be small and lightweight. The fuel feeding device also needs to be small, and there is a particular need for reduced cost in small-sized multi-purpose engines.